Method for Determining the Status of Cutterhead of Ultra-large Diameter Slurry Shield Tunnelling in Complex Geological Formations: A Case Study of Qingdao Jiaozhou Bay Second Submarine Tunnel

To address the challenge of real-time cutterhead condition assessment during the construction of super-large-diameter slurry shield tunnels in complex strata, this study, based on the Qingdao Jiaozhou Bay Second Subsea Tunnel Project, proposes a cutterhead condition assessment method utilizing the dynamic response of tunneling parameters. By analyzing the evolution patterns of key parameters, including total thrust force, cutterhead torque, and penetration rate, and introducing composite parameters (Torque-Penetration Ratio P and Thrust-Penetration Ratio Q), quantitative identification criteria for three typical cutterhead conditions were established: normal, mud cake formation, and tool wear. The results indicate that under mud cake conditions, the P and Q values exhibit stepwise mutations (with an average P value of 1.86), accompanied by a sharp increase in thrust force and torque, a significant drop in penetration rate, and a tool eccentric wear rate reaching 100%. Tool wear conditions can be further categorized into normal wear (stable parameters), single wear (abnormalities in thrust force only), and comprehensive wear (average P value of 0.95), with the latter requiring attention to sudden failures caused by parameter hysteresis. In practical application, a P value exceeding the historical threshold (>1.36) can serve as an early warning for impending tool failure, enabling preventive tool replacement to mitigate accident risks. The proposed assessment method has been successfully implemented on-site, significantly enhancing the efficiency of cutterhead anomaly response and management.